Designing Spinning Bloch States in 2D Photonic Crystals for Stirring Nanoparticles

Based on an optical analogy of spintronics, the generation of spinning Bloch states is theoretically investigated in two-dimensional photonic crystals without space-inversion symmetry. We address its close relation to the Berry curvature in crystal momentum space, which represents the nontrivial geometric property of a Bloch state. It is shown that the Berry curvature is easily controlled by tuning two types of dielectric rods in a honeycomb photonic crystal. Bloch states with large Berry curvatures appear as optical tornadoes in real space. The radiation force of such a configuration is analyzed, and its possible application for selective optical stirrer is discussed as a complementary proposal in optical tweezers technology.